Most women with breast cancer have hormone-receptor positive (HR+) disease. This means their cancer cells have receptors where hormones, like estrogen and progesterone, can attach. These hormones help the cancer cells to multiply quickly.
A woman whose breast cancer is hormone-receptor positive may have hormonal therapy. Hormonal therapy combats cancer by reducing or blocking the production or effects of hormones. Sometimes it is given following other treatments, such as surgery, chemotherapy, and radiation. Hormonal therapy reduces the risk of a recurrence of breast cancer and also reduces the risk of a new breast cancer in a woman who has had the disease. Recent research shows these drugs are also effective in helping prevent breast cancer in the first place among women at high risk.
If your cancer is not hormone-receptor positive, you will not benefit from hormonal therapy.
There are two main forms of hormonal therapy: estrogen-receptor blockers and aromatase inhibitors. Other hormonal therapies are used for breast cancer in certain circumstances.
Estrogen-receptor blockers block the effects of estrogen in the breast tissue. They are usually prescribed for premenopausal women and sometimes for postmenopausal women. Tamoxifen (Nolvadex) is a commonly prescribed estrogen-receptor blocker. Others are toremifene (Fareston) and raloxifene (Evista). These drugs are also known as selective estrogen-receptor modulators, or SERMs.
Aromatase inhibitors block the production of estrogen in the body. They are currently approved for use only in women who’ve gone through menopause (although in some clinical trials premenopausal women are being treated with aromatase inhibitors). Anastrazole (Arimidex), letrozole (Femara), and exemestane (Aromasin) are three commonly used aromatase inhibitors.